The Art of Assembly Language, 2nd Edition

4.29 Aligning Fields Within a Record

To achieve maximum performance in your programs, or to ensure that HLA's records properly map to records or structures in some high-level language, you will often need to be able to control the alignment of fields within a record. For example, you might want to ensure that a double-word field's offset is an even multiple of 4. You use the align directive to do this. The following example shows how to align some fields on important boundaries:

type
     PaddedRecord:
          record
               c:  char;
               align(4);
               d:  dword;
               b:  boolean;
               align(2);
               w:  word;
          endrecord;

Whenever HLA encounters the align directive within a record declaration, it automatically adjusts the following field's offset so that it is an even multiple of the value the ...